1. Field of the Invention
This invention relates to a vibratory parts feeder with a driver that includes a plurality of rotating eccentric weights.
2. Description of the Prior Art
A typical vibratory parts feeder is shown in U.S. Pat. No. 3,258,111. Such feeders include a base mass that is supported upon vibration isolators and a frame mass that is mounted above the base mass by at least three inclined leaf spring sets which enable rotational oscillatory movement of the frame mass in response to an exciter motor. Such exciter motors are commonly of an electromagnetic type that includes a field core and a coil mounted on the base mass. An armature is mounted on the underside of the frame mass with an air gap between opposing faces of the field core legs and the armature. When an alternating current is supplied to the coil, the armature and frame mass are alternately drawn toward the coil and released flexing the leaf spring sets. Thus, the frame mass oscillates about a central vertical axis at a predetermined frequency that is established by the frequency of the current supplied to the coil.
A problem encountered with such feeders is that they are difficult to make in large sizes because the air gap of the electromagnet is limited by the magnetic force available and thus, the gap must be relatively small. A small air gap necessitates a short stroke and a high frequency. Since high frequency operation can cause high stresses in the feeder structure, a massive structural design is needed for the feeder structure to be compatible with high frequency stresses.
U.S. Pat. No. 3,159,269 shows a driving arrangement for a material handling device. Reciprocating vertical force impulses that are generated by an air operated vibrator are applied through a mechanical linkage that includes a lever arm, to the underside of a feeder bowl. While this force transmitting linkage is not limited by an air gap, it does depend upon mechanical impact between components to create the vibration and such mechanical impact causes noise and wear of components.
U.S. Pat. No. 2,418,982 shows a rocking mixer that has a resiliently supported base member and a material container resiliently supported above the base member. A plurality of rotating eccentric weights are journalled in the base member to provide the vibratory driving force that produces either a rocking motion or a vertical translatory motion of the material container. While this driving arrangement eliminates mechanical impact between components, the rocking motion or vertical translatory motion produced would not be satisfactory for a feeder bowl that requires simultaneous rotational oscillation and vertical reciprocation.